The National Transportation Safety Board announced over the weekend that x-rays and CT scans of the lithium-ion battery pack that caught fire in a Boeing 787 Dreamliner in Boston recently was not overcharged. The battery in question powered the plane’s auxiliary power unit and the investigators have disassembled the battery and are still investigating some of the individual battery cells.

The battery fire has led airlines to stop flying the 787 planes around the world. The NTSB investigators have also said that they have examined several other components from the aircraft including battery management circuit boards and associated bundles of wire. The investigators also intend to continue testing components such as the battery charger and battery management unit.

The investigators have announced that the plane's flight data recorder indicates that the battery never exceeded its design voltage of 32 volts. The FAA issued a directive last week that the Boeing 787 Dreamliner should not fly until any problems with the battery packs are resolved.

Boeing has announced that it will halt deliveries of the 787 to customers while it works with the FAA to solve the battery issues. The batteries at the center of the investigation are lithium-ion units manufactured in Japan by GS Yusana under a subcontract to a company called Thales.

I agree. And not just vibration, but pressure and temperature extremes, all of which are not well tolerated by lithium (ion) cells. Lithium Polymer would be better suited but I'm sure Boeing chose Li-ion because of its more 'mature' industrial status.

All I can say: my Milwaukee 18v lithium drill battery only took a few drops before shorting out and failing, whereas my R/C Truck LiPo pack has taken impacts so harsh it has been ejected from the vehicle into a concrete wall, and it continues to function fine.

quote: not just vibration, but pressure and temperature extremes, all of which are not well tolerated by lithium (ion) cells

While that makes sense, one would assume that Boeing did a bunch of testing that exposed the batteries and the entire aircraft to those conditions - repeatedly. I'm very interested in hearing how they missed this problem in their testing.

quote: but I'm sure Boeing chose Li-ion because of its more 'mature' industrial status.

Battery choice was made in 2005-2006 timeframe and a contract was awarded. This was a multi-level contract in that Boeing (US) contracted Thales (France) who contracted Yusua (Japan).

This was before the Sony issue. At the time the initial choice was made, there was little conrete real world evidence that Lithium Cobalt Ion batteries were a potential problem. Once the contract is awarded, changing the details of the contract mean serious money. Without a "proven" safety risk, Boeing (management) wouldn't force Thales to change it's supplier.

quote: It seems that the batteries heated up in a self-accelerating pattern called thermal runaway. Heat from the production of electricity speeds up the production of electricity, and… you’re off. This sort of things happens in a variety of reactions, not just in batteries, let alone the Li-ion kind. But thermal runaway is particularly grave in Li-ion batteries because they pack a lot more power than the tried-and-true metal-hydride ones, not to speak of Ye Olde lead-acid.

So the IEEE is theorizing that thermals could be to blame. Makes more sense then most theories here.

The problem with the thermal theory is the cells at the end of the battery box seem to be the ones that have collapsed, which suggests they were the ones that actually failed, not the ones in the middle, which is where it would be hardest to dissipate heat.

The charging current is much more important than the voltage when dealing with these types of batteries. The lower the charge current, the less likely that the battery will fail. However, Boeing must balance the charge current versus the recharge time.

The vibration environment in a modern airliner is probably less than in most other vehicles. I would say that the vibration environment of the Chevy Volt battery is worse.

But due to the energy stored in lithium batteries, a failure of one cell would certainly lead to a failure of the entire battery in short order. Perhaps the 787 needs to have the battery cells in separate cases to limit the damage if one fails.

quote: The National Transportation Safety Board announced over the weekend that x-rays and CT scans of the lithium-ion battery pack that caught fire in a Boeing 787 Dreamliner in Boston recently was not overcharged.

Sometimes, DT's descent into being incapable of using a spellcheck can be humorous.